1. Field of the Invention
The present invention relates to a printer and a printing method and, more particularly, to a technique for printing both sides of a printing medium.
2. Description of the Related Art
As a printer for printing both sides of a printing medium, a thermal printer provided with first and second platen rollers, and first and second thermal heads opposed to the platen rollers, for printing front-back both sides of a printing medium such as thermal recording paper is proposed as is described in Jpn. Pat. Appln. KOKAI Publication No. 9-58034. In this thermal printer, the first and second platen rollers rotate in synchronization with each other, and feed the printing medium at the same feed rate. When the printing medium passes through a part between the first platen roller and the first thermal head, printing is performed by the first thermal head on one surface (for example, a front surface) thereof. When the printing medium passes through a part between the second platen roller and the second thermal head, printing is performed by the second thermal head on the other surface (for example, a back surface) thereof.
However, there is the following problem in the above-mentioned technique. That is, because of the structure of the printer, two thermal heads cannot be provided at the same position. Hence, when printing processing is started at the same time on the front and back surfaces of the printing medium, the printing start position differs between the front and back surfaces due to the difference in the position of the thermal head. In consideration of the above fact, there is proposed a printer in which timings of printing processing of both the thermal heads are adjusted in order to line up printing start positions on the front and back surfaces. However, in a printer in which timings of printing processing performed by a plurality of heads are adjusted, there is a problem that an algorithm of printing control becomes complicated.
Thus, in the present invention, an object thereof is to provide a printer and a printing method capable of lining up printing start positions on both surfaces of the printing medium by a simple algorithm.